Need help to ID part

[glebreton]

I am trying to improve the suspension on 01 Excursion LTD 4X4 7.3L. I got under the rear end today and I see what looks like an add-a-leaf under the stock rear leaf springs. I looked for pics online but most stock pics do not show this extra lower spring arm. I took some pics that are so-so. Can anyone tell if this is a stock spring or an aftermarket assist. The spacers or bump stops at the end of this addtl spring leaf are worn and need replacing. As best I can tell, it reads "565 234" on the spacer. I can't find that as an OEM ford part to get a replacement. I'd appreciate any help determining if this is aftermarket addition and how to find a replacement spacer/bump stop for this lower spring arm. I hope the pics are helpful. Thanks in advance.